High speed surgical cutting instrument

ABSTRACT

A surgical cutting instrument including an outer tube having a bearing sleeve disposed within a lumen thereof, along with an inner wire assembly extending through the outer tube and the bearing sleeve. A cutting tip is connected to the inner wire assembly distal the outer tube. Conversely, a coupling chuck is connected to a proximal section of the inner wire assembly, with a housing maintaining the outer tube and the coupling chuck. When mounted to a motor, the inner wire assembly is rotated to effectuate a surgical cutting procedure at the cutting tip, with the bearing sleeve supporting the inner wire assembly relative to the outer tube during rotation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/444,121, filed May 31, 2006, entitled “HIGH SPEED SURGICAL CUTTINGINSTRUMENT”, which is a continuation-in-part of U.S. application Ser.No. 10/776,835, filed on Feb. 11, 2004, entitled “HIGH SPEED SURGICALCUTTING INSTRUMENT,” the teachings of which are incorporated herein byreference.

BACKGROUND

The present invention relates to a surgical cutting instrument. Moreparticularly, it relates to a high speed surgical cutting instruments,such as a bone-cutting bur, usable with various size cutting tips andadapted for minimal interference with surgical site visibility.

Surgical cutting instruments including a cutting tip are usuallyconnected to a motorized handpiece for rotating the cutting tip atvarious speeds to perform a variety of surgical cutting procedures. Manyhigh speed surgical cutting instrument designs impair visibility of asurgical site during a cutting procedure. For example, high speedsurgical cutting instruments often employ a straight bur extenderincluding a ball bearing assembly between an outer support sleeve and arotating inner cutter shaft. Outer diameters of such outer supportsleeves are relatively large (e.g., on the order of 6 mm) to accommodatea ball bearing assembly. Such relatively large outer diameters createblind spots and otherwise impair surgical site visibility duringcutting. Other line-of-sight and handling concerns are often encounteredwith straight bur extenders. For example, the straight support sleevesassociated with straight bur extenders are typically in or near asurgeon's line of sight during cutting.

In view of the above, it would be desirable for a surgical cuttinginstrument to have a reduced diameter and/or angle or bend away from anassociated handpiece to improve visibility, ergonomics, or otherperformance or cost factors. Additionally, it would be desirable toprovide a curved bur extender operable at relatively high speeds withsmall burs (e.g., about 2 mm) as well as larger burs (e.g., burs havingdiameters greater than about 2 mm, from about 3 mm to about 4 mm, or atleast about 3 mm).

SUMMARY

Some aspects in accordance with principles of the present inventionrelate to a surgical cutting instrument for use with a motor having adrive mechanism. The surgical cutting instrument includes an outer tube,a bearing sleeve, an inner wire assembly, a cutting tip, a couplingchuck, and a housing. The outer tube defines a proximal regionterminating at a proximal end, a distal region terminating at a distalend, and a lumen extending from the proximal end to the distal end. Thebearing sleeve is substantially tubular in shape, and defines a proximalterminus, a distal terminus, and an inner passage. At least a portion ofthe bearing sleeve is secured within the lumen of the outer tube. Theinner wire assembly defines a proximal section and a distal section, andextends through the lumen of the outer tube and through the innerpassage of the bearing sleeve. The cutting tip is connected to thedistal section of the inner wire assembly. Conversely, the couplingchuck is connected to the proximal section of the inner wire assemblyand is adapted for connection to a drive mechanism of a motor. Finally,the housing maintains the proximal region of the outer tube and thecoupling chuck, and is adapted for connection to a motor. With thisconfiguration, the bearing sleeve supports the inner wire assembly uponrotation thereof relative to the outer tube during a cutting operation.In some embodiments, the cutting tip has a relatively large outerdimension (e.g., on the order of at least 3 mm), with the bearing sleeveminimizing vibration of the cutting tip.

Other aspects in accordance with principles of the present inventionrelate to a method of performing a surgical drilling procedure on bodilymaterial at a target site of the patient. The method includes providinga surgical cutting instrument as described above. The bodily material atthe target site is exposed, and the cutting tip is deployed against thebodily material. The inner wire assembly is rotated within the outertube and the bearing sleeve to initiate a cutting interface between thecutting tip and the bodily material in contact therewith. In thisregard, the distal section of the inner wire assembly is maintained bythe bearing sleeve, and the proximal section of the inner wire assemblyis maintained by the outer tube during rotation thereof. In someembodiments, the inner wire assembly is rotated at speeds of at leastabout 50,000 RPM. In other embodiments, the methodology is performed aspart of an acoustic neuroma surgery.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a surgical cutting instrument inaccordance with principles of the present invention.

FIG. 2 is an exploded, cross-sectional view of the surgical cuttinginstrument of FIG. 1 in an unassembled form.

FIG. 3A is a perspective view of a bearing sleeve portion of the cuttinginstrument of FIG. 1.

FIG. 3B is an end view of the bearing sleeve of FIG. 3A.

FIG. 4 is an enlarged cross-sectional view of the surgical cuttinginstrument of FIG. 1.

FIG. 5 is a schematic view illustrating a method of connecting an innerwire assembly to a coupling chuck of the surgical cutting instrument ofFIG. 1.

FIG. 6 is a cross-sectional view of a surgical cutting instrument inaccordance with principles of the present invention.

FIG. 7 is an enlarged cross-sectional view of the surgical cuttinginstrument of FIG. 5.

FIG. 8 is a cross-sectional view of a surgical cutting instrument inaccordance with principles of the present invention.

FIG. 9A is cross-sectional view of a surgical cutting instrument inaccordance with principles of the present invention.

FIG. 9B is an enlarged cross-sectional view of the surgical cuttinginstrument of FIG. 9A designated by the circle 9B.

DETAILED DESCRIPTION

Embodiments of high speed surgical cutting instruments in accordancewith the present invention are to be understood cumulatively, as awhole, with features and principles of operation treated interchangeablyas desired. With this in mind, a surgical cutting instrument 20 inaccordance with principles of the present invention is shown in FIG. 1.The surgical cutting instrument 20 includes an outer support tube 22, abearing sleeve 24, an inner wire assembly 26, a cutting tip 28, acoupling chuck 30, a housing 32, and an evaporative cooling sleeve 34.In general terms, the evaporative cooling sleeve 34 is secured over aportion of the outer tube 22. The bearing sleeve 24 is secured in theouter tube 22 with portions of the inner wire assembly 26 coaxiallydisposed within the bearing sleeve 24 and the outer tube 22,respectively.

The cutting tip 28 is connected to, and extends distally from, the innerwire assembly 26. The coupling chuck 30 is secured to the inner wireassembly 26 and is adapted for connection to a drive mechanism (notshown) of a motor (not shown). The housing 32 maintains the outer tube22 and the coupling chuck 30, and is also adapted for connection to amotor.

As will be described in greater detail, some embodiments include thebearing sleeve 24 maintaining a portion of the inner wire assembly 26and journal bearing being established between a portion of the innerwire assembly 26 and the bearing sleeve 24 upon rotation of the innerwire assembly 26 relative to the bearing sleeve 24. A journal bearing isalso optionally established between a portion of the outer tube 22 andthe inner wire assembly 26 upon rotation of the inner wire assembly 26relative to the outer tube 22. As described in greater detail below, theinstrument 20 and components thereof optionally provide one or morefeatures that facilitate extremely high rotational speeds (e.g.,including at least about 50,000 RPM and on the order of about 80,000RPM) of a relatively large cutting tip 28 in the form of a bur,including, for example bur cutting tips having an outer diameter greaterthan about 2 mm, from about 3 mm to about 4 mm, or at least about 3 mm.Additionally, the outer tube 22 and the inner wire assembly 26 defineone or more curved segments as desired.

FIG. 2 illustrates the surgical cutting instrument 20 in an unassembledstate from an exploded, cross-sectional view. With reference to FIG. 2,the outer tube 22 is substantially elongate and tubular in shape. Theouter tube 22 defines a proximal end 40, a distal end 42, a proximalregion 44 terminating at the proximal end 40, and a distal region 46terminating at the distal end 42. The outer tube 22 also includes anintermediate region 48 extending between the proximal and distal regions44, 46. The outer tube 22 defines one or more inner diameters with alumen 50 extending from the proximal end 40 to the distal end 42 at aninner surface 52 of the outer tube 22.

The outer tube 22 assumes a variety of longitudinal shapes as desired.For example, the outer tube 22 optionally defines a curved profile at oralong one or both of the intermediate region 48 and the distal region46. In some embodiments with a curved or bent profile, the distal region46 is angularly offset from the proximal region 44. For example, theouter tube 22 extends through a radius of curvature from about 3 inches(about 76 mm) to about 6 inches (about 152 mm), although otherdimensions are contemplated. In addition, the outer tube 22 isoptionally constructed to facilitate formation of a rotating journalbearing (i.e., frictional sliding journal bearing) relative to the innerwire assembly 26 in a straight configuration or in conjunction with acurved configuration.

The proximal region 44 of the outer tube 22 is adapted to be received inthe housing 32. Some embodiments include the proximal region 44 beingsubstantially straight and uniform in outer diameter. For example, theouter diameter of the proximal region 44 is about 0.090 inch (about 2.3mm), although other dimensions, such as tapers or other features arealso contemplated.

The intermediate region 48 of the outer tube 22 can form a shoulder 56that abuts the housing 32 upon final assembly. Some embodiments includea remainder of the intermediate region 48 extending distal the housing32 upon final assembly) at a uniform outer diameter of about 0.110 inch(about 2.79 mm), including at a curved segment 54 and one or morestraight segments, if desired.

The distal region 46 optionally tapers in outer diameter to the distalend 42. For example, the outer tube 22 tapers from an outer diameter ofabout 0.110 inch (about 2.79 mm) to a diameter of about 0.72 inch (about18.3 mm) at the distal end 42, although other dimensions are alsoacceptable. Alternatively, the distal end 42 can be substantially freeof any tapers.

The outer tube 22 defines one or more inner diameters along the lumen50. For example, the lumen 50 is optionally defined by two or morelengths having different diameters. In the configuration of FIG. 2, thelumen 50 includes or is defined by a first segment 60 having a firstdiameter and a second segment 62 having a second diameter. However, aswill be described in greater detail, some embodiments include the lumen50 varying in diameter over three or more segments if desired.Regardless, the first segment 60 originates at the distal end 42 andextends proximally along the distal region 46. The second segment 62extends proximal from the first segment 60 through a remainder of theouter tube 22 to the proximal end 40. The first segment 60, includingthe first diameter, is adapted to receive at least a portion of thebearing sleeve 24, for example via a press fit. In some embodiments, thefirst segment 60 has a length in the range of 0.35-0.65 inch (about8.9-16.5 mm), for example 0.47 inch (11.9 mm), and a diameter in therange of 0.04-0.08 inch (1.0-2.0 mm), for example 0.06 inch (1.5 mm); byway of reference, a diameter of the second segment 62 is in the range of0.02-0.06 (0.51-1.5 mm), for example, 0.037 inch (0.94 mm). It will beunderstood, however, that other dimensions are also contemplated.

Where the inner wire assembly 26 is relatively small in outer diameter,the lumen 50 is relatively small in diameter. It should be understoodthat reducing diameter size of the lumen 50 facilitates reduction of anoverall outer diameter of the outer tube 22 while retaining sufficientwall thickness to help ensure desired strength and rigidity of the outertube 22. As previously alluded to, reducing the outer diameter of theouter tube 22 facilitates an ability of a surgeon or other operator tosee a surgical cutting site during a cutting operation. For example,portions of the outer tube 22 extending distal to the housing 32(including or excluding the shoulder 56) define, in some embodiments, amaximum outer diameter of no more than about 0.125 inch (about 3.18 mm),although other dimensions are contemplated. The outer tube 22 isoptionally constructed of a material selected to provide the outer tube22 with high strength, high stiffness characteristics while satisfyingdimensional and curvature constraints. For example, the outer tube 22 isformed of conventional surgical instrument materials, such as stainlesssteel.

The inner surface 52 of the outer tube 22 can be highly polished tofacilitate formation of a rotating journal bearing subsequentlydescribed in greater detail. More particularly, it has surprisingly beenfound that polishing the inner surface 52 of the outer tube 22 to asurface roughness of not greater than 20μ, inch, and in someembodiments, not greater than 10μ, inch, facilitates viability of thesurgical cutting instrument 20 incorporating the curvature anddimensional characteristics at high operational speeds. However, otherembodiments include the inner surface 52 being relatively less polishedor unpolished.

The bearing sleeve 24 can be an elongate, tubular body defining aproximal terminus 64, a distal terminus 66, and an inner passage 68extending from the proximal terminus 64 to the distal terminus 66. Withthis construction, the bearing sleeve 24 forms or provides a bearingsurface along the inner passage 68. Additionally, the bearing sleeve 24is adapted to be inserted into the outer tube lumen 50 at the distal end42 of the outer tube 22 (e.g., within the first segment 60 of the lumen50). For example, the bearing sleeve 24 is optionally sized to be pressfit, or otherwise define an interference fit, within the outer tubelumen 50 at the distal end 42. The inner passage 68 is shown generallyas extending for a substantially continuous diameter; however, it shouldbe understood that other features, for example stepped diameters orother selected variations in the inner passage diameter, are alsocontemplated.

The bearing sleeve 24 is substantially cylindrical and circular intransverse cross-section, though other shapes, such as ellipsoid, forexample, are also contemplated. In some embodiments, the bearing sleeve24 has a length in the range of about 0.25-0.65 inch (about 6.35-16.5mm), for example, 0.46 inch (11.7 mm); and an inner diameter in therange of about 0.02-0.06 inch (0.51-1.5 mm), for example 0.038 inch(0.97 mm); although other dimensions are contemplated. An outer diameterof the bearing sleeve 24 can be sized in accordance with the outer tubelumen 50 (e.g., at or along the first segment 60) so as to facilitate apress fit or interference fit. In this regard, and with reference toFIGS. 3A and 3B, the bearing sleeve 24 can include a plurality oflongitudinal ribs 69 a projecting from an exterior surface 69 b. Theribs 69 a combine to define an effective outer diameter approximating orslightly larger than the corresponding diameter of the outer tube lumen50 (FIG. 2), for example in the range of 0.041-0.081 inch (1.04-2.06mm), and can be 0.061 inch (1.55 mm). The bearing sleeve 24 outerdiameter at the exterior surface 69 b is slightly less than theeffective outer diameter defined by the ribs 69 a (e.g., on the order of0.001-0.01 inch (0.025-0.25 mm) less). The circumferential spacingbetween the ribs 69 a facilitates ease of press-fit assembly into theouter tube lumen 50 as the ribs 69 a can more easily deform to accountfor tolerance variations. The ease of assembly can be further enhancedby the ribs 69 a terminating distal the proximal terminus 64 (that isotherwise initially inserted into the outer tube lumen 50 duringassembly). Further, upon final assembly, a slight air gap is establishedbetween the inner surface 52 (FIG. 2) of the outer tube 22 and theexterior surface 69 b of the bearing sleeve 24, with this air gapassisting in cooling during use. Alternatively, the ribs 69 a can beeliminated.

The bearing sleeve 24 can be formed from a variety of materialscompatible with high speed rotation of the inner wire assembly 26,selected to exhibit low wear and low temperature characteristics in thepresence of the rotating wire assembly 26. To this end, a material ofthe bearing sleeve 24 is, in some embodiments, selected to be a low wearmaterial that will not generate adverse debris (e.g., black in color)when subjected to a high speed rotation of the otherwise metallic innerwire assembly 26, and thus is in one embodiment formed from a materialother than metal. For example, the bearing sleeve 24 is formed of amaterial including one or more of the following: polyetheretherketone(PEEK); PEEK with carbon additives; PEEK with polytetrafluoroethylene(PTFE) and carbon additives; PTFE, including PTFE with variousadditives; ceramics, such as sapphire, for example. In otherembodiments, the bearing sleeve 24 can be formed of a surgically-safemetal.

Returning to FIG. 2, the inner wire assembly 26 includes a proximalsection 70, a distal section 72, and an intermediate section 74, theintermediate section 74 between the proximal section 70 and the distalsection 72. In some embodiments, the inner wire assembly 26 has anoverall longitudinal length greater than that of the outer tube 22 suchthat upon final assembly, the proximal and distal sections 70, 72 extendfrom the proximal and distal ends 40, 42, respectively, of the outertube 22.

The proximal section 70 is generally adapted to be connected to thecoupling chuck 30, as will be subsequently described in greater detail.In turn, the distal section 72 is adapted to be connected to the cuttingtip 28, as will also be described in greater detail. The intermediatesection 74 is generally adapted to provide a flexible, mechanicalconnection between the proximal and distal sections 70, 72 such thatrotation of the proximal section 70 translates to rotation of the distalsection 72, and thus, the cutting tip 28. Some embodiments includeforming the intermediate section 74 to define a length at least as longas an extension of the curved section 54 of the outer tube 22. Forexample, the intermediate section 74 is optionally formed to have amargin at each end, such that the intermediate section 74 is somewhatlonger than the curved section 54 or curved sections where appropriate.Such “over sizing” of the intermediate section 74 optionally helpsensure that the inner wire assembly 26 does not bind with the outer tube22, for example.

As previously alluded to, the intermediate section 74 can be moreflexible than at least one of the proximal section 70 and the distalsection 72. For example, the intermediate section 74 optionally definesa substantially smaller diameter than one or both of the proximalsection 70 and the distal section 72 in order to provide relatively moreflexibility to the intermediate section 74, for example. The diameter ofthe intermediate section 70 can be selected to be smaller than that ofthe proximal section 70 and the distal section 72, in part, because theintermediate section 74 does not support bending loads induced by thecutting tip 28 to the same extent as the distal section 72.Additionally, or alternatively, the intermediate section 74 is formed ofmore flexible materials than one or both of the proximal section 70 andthe distal section 72 or includes other features to promote flexibility.By way of non-limiting examples, the diameter of the proximal and distalsections 70, 72 is in the range of about 0.025-0.045 inch (0.635-1.14mm), for example 0.035 inch (0.89 mm); whereas the diameter of theintermediate section 74 can be in the range of about 0.015-0.035 inch(0.38-0.89 mm), for example 0.024 inch (0.61 mm), it being understoodthat a variety or other dimensions are also contemplated. For example,in alternative embodiments, the inner wire assembly 26 has a uniformdiameter.

The inner wire assembly 26 is optionally adapted to facilitateestablishment of a rotating journal bearing relative to the outer tube22 and the bearing sleeve 24. In some embodiments, the additionalflexibility of the intermediate section 74 facilitates rotation of theintermediate section 74 within the outer tube 22 at the curved section54. For example, flexibility of the intermediate section 74 has thepotential to reduce fatigue effects on the inner wire assembly 26,binding of the inner wire assembly 26 within the outer tube 22, forexample proximate the curved segment 54, and/or overall resistance torotation of the inner wire assembly 26 while in a bent configuration. Arelatively larger diameter, and therefore rigidity, of the proximalsection 70 optionally provides additional structural support forconnection to the coupling chuck 30, as well as a more stable journalbearing within the outer tube 22. Additionally, a relatively largerdiameter of the distal section 72 provides additional structural supportfor the cutting tip 28 (e.g., when subjected to bending loads and/orimpact chatter loads during cutting), as well as a more stable journalbearing within the bearing sleeve 24 as desired.

Diametric clearances between the outer tube lumen 50 and the inner wireassembly 26, and bearing sleeve inner passage 68 and the inner wireassembly 26, are optionally selected to promote reduced potential forbinding and establishment of effective journal bearings. For example,the outer diameter of the proximal section 70 of the inner wire assembly26 can be about 0.001-0.005 inch (0.025-0.127 mm), for example 0.002inch (0.05 mm) less than the diameter of the second segment 62 of theouter tube lumen 50. In turn, the outer diameter of the distal section72 of the inner wire assembly 26 can be about 0.001-0.005 inch(0.025-0.127 mm), for example 0.002 inch (0.05 mm), less than thediameter of the inner passage 68 of the bearing sleeve 24. Conversely,the outer diameter of the intermediate section 74 can be about0.005-0.025 inch (0.127-0.635 mm), for example 0.013 inch (0.33 mm),less than the diameter of the second segment 62 of the outer tube lumen50, for example. It will be understood, however, that other dimensionsare also contemplated.

As alluded to above, the inner wire assembly 26 is generally formed toexhibit high strength and good fatigue characteristics. Fatigue strengthis a function of material selection and end geometry, as well as othervariables. In some embodiments, the inner wire assembly 26 is formed toexhibit a fatigue strength or endurance limit of at least about 75 Kpsiwhere the outer tube 22 imparts a curve onto a longitudinal length ofthe inner wire assembly 26. It has surprisingly been found that suchfatigue strength characteristics and dimensions are optionally achievedwith an appropriate tool steel material, such as M-series tool steels(molybdenum high speed tool steels), A-series tool steels (medium-alloyair-hardening cold work tool steels), and others.

For example, the inner wire assembly 26 can be a homogenous, one-piecewire M2 tool steel. Alternative other materials exhibiting the desireddurability and fracture resistance are employed for the inner wireassembly 26, including, for example, other tool steels; 304V hightensile strength drawn wire; other steel wire materials subjected to aroll burnishing process that improves the fatigue strength of the wireby putting the outer surface into a state of compression; other steelwire materials subjected to ultrasonic shot peening or laser shotpeening for improving fatigue strength of the wire by putting the outersurface into a state of compression; and others. Even further, in someembodiments other non-steel metals such as iridium, osmium, or rutheniumare optionally employed, as are ceramics such as silicon carbide,silicon nitride, boron carbide, titanium carbide, tungsten carbide, andothers. Conventional materials that do not otherwise conform to theabove-described strength and stiffness parameters can also be employed.

To further enhance wear resistance properties of the inner wire assembly26, the inner wire assembly 26 can be subjected to processing (e.g.,heat treated) and/or coated with additional material(s), resulting in aRockwell Hardness of not less than 50 HRC or not less than about 60 HRC,for example, although other characteristic Rockwell Hardness values arealso contemplated. Some embodiments include employing a hardenedmaterial (not shown) coating to provide a dense carbon finish to theinner wire assembly 26. For example, the hardened material coating canbe a dense carbon (diamond-like coating), coated to a thickness of notmore than about 0.3 mm, although other dimensions are contemplated.Other coating materials are also optionally employed, such as, forexample, zirconium nitride, chrome, polytetrafluoroethylene (PTFE) orother fluorocarbon materials, titanium nitride, electroless nickelimpregnated with PTFE, and others.

The cutting tip 28 can assume a variety of forms and generally includesa cutting bur 76 and an attachment end 78 adapted for connection to thedistal section 72 of the inner wire assembly 26. The attachment end 78can be configured to coaxially receive the distal section 72 of theinner wire assembly 26. Regardless, the inner wire assembly 26 is can beconnected to attachment end 78 via a number of known processes such as,for example, laser welding, brazing, press fitting, thermal shrinkfitting, adhesive, and others. Alternatively, the attachment end 78 ofthe inner wire assembly 26 and the cutting tip 28 can be connected byintegrally forming the distal section 72 of the inner wire assembly 26and the cutting tip 28 (see, e.g., cutting instrument 120 of FIG. 5).For example, the inner wire assembly 26 and the cutting tip 28 areoptionally machined from a single piece of stock material. The cuttingbur 76 optionally defines an outer diameter of greater than about 2 mm,an outer diameter from about 3 mm to about 4 mm, or an outer diameter ofabout 3 mm or more, for example, although other dimensions arecontemplated. In particular, the cutting bur 76 optionally assumes avariety of shapes and sizes known in the art (e.g., 3 mm fluted, 4 mmdiamond and others).

The coupling chuck 30 is generally configured to facilitate connectionof the motor drive mechanism (not shown) to the inner wire assembly 26.As a point of reference, each of the motor (not shown) and the drivemechanism assumes a variety of forms as desired. For example, the motoris optionally of a type typically employed with surgical cuttinginstruments, such as electric, battery powered or pneumatic. Also, anyother type of motor or drill drive system is employed as desired.Similarly, the drive mechanism is optionally of a type typicallyemployed with surgical cutting instruments that facilitate connection orcoupling to the cutting device, such as mechanical connection, anon-contacting magnetic connection, a non-contacting air driven coupling(e.g., an air vane), and others. With this in mind, the coupling chuck30 is adapted for use with a mechanical-type drive mechanism, it beingunderstood that the coupling chuck 30 is can be configured in accordancewith any other type of drive mechanism.

The coupling chuck 30 defines a proximal end 80, a distal end 82, aproximal portion 84 extending to the proximal end 80, and a distalportion 86 extending to the distal end 82. The distal portion 86 forms afirst passage 88 originating at the distal end 82. The first passage 88is sized to receive the proximal section 70 of the inner wire assembly26. The proximal portion 84 can further form a second passage 90extending proximally from the first passage 88 to the proximal end 80.The second passage 90 is sized to coaxially receive and maintain theproximal section 70 of the inner wire assembly 26. Alternatively, (see,e.g., surgical cutting instrument 320 of FIG. 8A), the second passage 90can terminate distal the proximal end 80 of the coupling chuck 30 as aclosed, blind hole.

Some embodiments include the proximal portion 84 forming a groove 92 anda tang 94 each adapted to facilitate coupling to the drill motor driveshaft (not shown). The tang 94 is of a reduced diameter, and serves as aguide surface that promotes rapid, consistent assembly of the drivemechanism to the coupling chuck 30. However, the coupling chuck 30assume a variety of other configurations, and assembly of the couplingchuck 30 to the outer tube 22 and/or the inner wire assembly 26 is alsooptionally varied as desired. For example, the coupling chuck 30 can bean integrally formed part of the inner wire assembly 26.

Similarly to the coupling chuck 30, the housing 32 can assume a varietyof forms and is generally configured to support the outer tube 22 aswell as facilitate connection of the coupling chuck 30, and thus theinner wire assembly 26, to a motor (not shown). The housing 32 can forma central aperture 100 having an open proximal end 102. The centralaperture 100 is sized to receive at least a portion of the motor. Thehousing 32 is configured to facilitate attachment to the drill motor viasnap fit, threads, interference fit, and others. The housing 32 definesa passage 106 fluidly connected to the aperture 100. The passage 106 issized to maintain the outer tube 22, and can be formed during an insertmolding procedure or otherwise. For example, the housing 32 isoptionally insert molded over the outer tube 22. Also, a variety ofother assembly techniques for connecting the outer tube 22 and thehousing 32 can be employed, such as gluing, welding, press-fitting,thermal shrink fitting, and others.

In some embodiments, the evaporative cooling sleeve 34 (FIG. 1) isprovided and is secured or formed over an exterior of the outer tube 22and extends from the proximal the housing 32 to the distal region 46.The cooling sleeve 34 is formed of a variety of materials, for examplefabric material such as nylon, silk, polypropylene, polyester, cotton,and others. In particular, the cooling sleeve 34 is optionally uncoatednylon. Regardless, the cooling sleeve 34 can readily conform to anycurved segment(s) defined by the outer tube 22. For example, the coolingsleeve 34 is constructed as a braided tube or a coil of thread wounddirectly onto the outer tube 22. The cooling sleeve 34 is optionallysecured over the outer tube 22 via a variety of means. For example,opposing ends of the cooling sleeve 34 are secured to the outer tube 22by clamping or adhesive as desired. The cooling sleeve 34 is generallyconstructed to absorb fluids (e.g., bodily fluids at a surgical site,irrigation fluids delivered during a surgical procedure, and others) andin operation wicks absorbed fluids toward the housing 32. In otherwords, fluids absorbed by the cooling sleeve 34, for example proximatethe distal end 42 of the outer tube 22, are conducted proximally by thecooling sleeve 34 toward the proximal region 44 of the outer tube 22until a substantial portion or an entirety of the cooling sleeve 34 issaturated. While the cooling sleeve 34 is shown in FIG. 1 as extendingalong a substantial length of the outer tube 22, the cooling sleeve 34need not extend to the housing 32. Further, the cooling sleeve 34 can beconstructed and sized to encompass an entirety of the outer tube 22.

During use, fluids absorbed by the cooling sleeve 34 evaporate via heatgenerated by rotation of the inner wire assembly 26 (FIG. 1) relative tothe outer tube 22, serving to cool the outer tube 22. With thisconstruction, as the outer tube 22 conducts more heat, the evaporativeprocess facilitated by the cooling sleeve 34 becomes more aggressive,regulating a surface temperature of the outer tube 22 to a relativelyconsistent level, for example. In operation, it has been surprisinglyfound that regardless of a temperature of the outer tube 22, the coolingsleeve 34 serves to cool the outer tube 22 to a substantially nominaltemperature (within 10° C.), in the presence of fluids. Regardless, anenhanced cooling effect is provided in conjunction with fluids proximatethe surgical site. Alternatively, however, the cooling sleeve 34 can beeliminated.

With respect to assembly of the outer tube 22 and the inner wireassembly 26, a lubricant (not shown) is optionally provided in the outertube lumen 50 along a length of an interface between the inner wireassembly 26 and the outer tube 22. The lubricant can facilitateformation of a hydrodynamic journal bearing between the outer tube 22and the inner wire assembly 26. In particular, the inner wire assembly26 is supported by a hydrodynamic effect and effectively “floats”relative to the outer tube 22 upon rotation of the inner wire assembly26 as desired. Lubricant is also optionally disposed in the bearingsleeve inner passage 68 along a length of an interface between the innerwire assembly 26 and the bearing sleeve 24 to provide a substantiallysimilar hydrodynamic effect between the bearing sleeve 24 and the innerwire assembly 26 as desired.

With this in mind, the lubricant can be a grease lubricant. Thelubricant can exhibit a dynamic viscosity of at least about 100 mm²/s at40° C.; or from about 150 mm²/s at 40° C. to about 250 mm²/s at 40° C.,and is hydrophobic in nature. One acceptable grease lubricant is asynthetic hydrocarbon material thickened with silica available, forexample, from Nye Lubricants, Inc., of Fairhaven, Mass., under the tradename “Nye NYOGEL® 670.” Also, other lubricant materials, such ascommercially available greases, can be employed as desired.Alternatively, the lubricant can be eliminated.

With reference to FIG. 4, assembly of the surgical cutting instrument 20toward the distal end 42 of the outer tube 22 can be described ingreater detail. The surgical cutting instrument 20 is assembled bycoaxially disposing the bearing sleeve 24 in the outer tube lumen 50.For example, the bearing sleeve 24 is optionally press fit or defines aninterference fit with the outer tube 22. The bearing sleeve 24 issecured in the outer tube lumen 50 (e.g., at the first segment 60 bestshown in FIG. 2) such that the bearing sleeve 24 and the outer tube 22are substantially rotationally fixed relative to one another.Additionally, the bearing sleeve 24 can be entirely received in thelumen 50. For example, the bearing sleeve 24 can have substantially thesame length as the first segment 60 of the lumen 50 such that when thebearing sleeve 24 is inserted into the outer tube lumen 50, the distalterminus 66 of the bearing sleeve 24 and the distal end 42 of the outertube 22 are substantially coterminous. Further, some embodiments includethe inner passage 68 and the second segment 62 of the lumen 50 definingsubstantially the same diameter, such that there is a substantiallycontinuous effective inner diameter from the inner passage 68 of thebearing sleeve 24 to the lumen 50 of the outer tube 22 at the secondsegment 62 of the lumen 50. Alternatively, a stepped-diametertransition, for example, is also contemplated (see, e.g., surgicalcutting instrument 120 of FIG. 5).

With reference to FIG. 1, the inner wire assembly 26 is generallydisposed within the lumen 50 (FIG. 2) of the outer tube 22. Aspreviously described, a lubricant (not shown), such as a greaselubricant, can optionally be disposed along at least a portion or anentirety of the interface between the inner wire assembly 26 and theinner surface 52 (FIG. 2) of the outer tube 22, as well as between theinterface between the bearing sleeve 24 and the inner wire assembly 26.With configurations in which the outer tube 22 includes or forms atleast one curved segment 54, upon placement of the inner wire assembly26 within the outer tube 22, the inner wire assembly 26 assumes a shapeof the outer tube 22, and thus, the curved segment 54. With this inmind, the outer tube 22/inner wire assembly 26 can assume a variety oflongitudinal shapes including one or more curved segments (for example,at the curved segment 54) and one or more straight segments.

With reference to FIG. 4, at least a portion of the distal section 72 ofthe inner wire assembly 26 is optionally disposed in the inner passage68 of the bearing sleeve 24 and extends distally from the outer tube 22and the bearing sleeve 24. The distal section 72 of the inner wireassembly 26 can be maintained by the bearing sleeve 24 such that thedistal section 72 of the inner wire assembly 26 does not contact theinner surface 52 of the outer tube 22 upon rotation of the inner wireassembly 26 and/or while the inner wire assembly 26 is stationary. Thus,the bearing sleeve 24 serves to maintain the distal section 72 of innerwire assembly 26 such that any contact (incidental or intentional) is atthe interface between the bearing sleeve 24 and the distal section 72,rather than contact between the outer tube 22 and the distal section 72.

In some embodiments, the distal section 72 of the inner wire assembly 26is supported by the bearing sleeve 24 in a substantially linearconfiguration that is free of overt bends or curves. As alluded toabove, the distal section 72 of the inner wire assembly 26 is optionallysubstantially thicker in diameter than the intermediate section 74, suchthat the distal section 72 is more structurally rigid than theintermediate section 74, and thus more suited to rotation within asubstantially linear, or straight, portion of the outer tube 22.

Increasing the diameter of the distal section 72 of the inner wireassembly 26 and/or use of the bearing sleeve 24 serves several purposes.For example, increasing a thickness of the distal section 72 canincrease rigidity of the assembly proximate the cutting tip 28. Thus,the assembly includes greater resistance to bending forces encounteredat the cutting tip 28 during a cutting operation as desired. Also,adding rigidity is often particularly advantageous as cutting tip sizeincreases (e.g., cutting burs of greater than about 2 mm, cutting bursfrom about 3 mm to about 4 mm, or cutting burs at least about 4 mm).With increased mass and/or size, inertial forces are potentiallyincreased at the cutting tip 28, resulting in a potential for greatervibration or other undesirable transverse movement at the cutting tip28. Such undesirable movement often results in more difficult cuttingoperations, increased fatiguing of the inner wire assembly 26, increaseddebris, increased temperatures, or other factors reducing cuttingoperation efficacy in general. Further, where the selected cutting tip28 has an increased size, chatter loads on the cutting tip 28 will alsoincrease, which in turn increases the bending stress and impact loads onthe distal section 72 of the inner wire assembly 26. The increaseddiameter of the distal section 72, in accordance with some embodiments,reduces the stress to more acceptable levels.

According to the examples of undesirable effects described above,vibration or movement makes it more difficult to accurately cut along adesired cutting path without unwanted deviations. Additionally,vibrations and increased bending due to transverse movement frominertial effects, including increases in both periodicity and degree ofbend, result in greater component fatigue. Undesirable movement at thecutting tip 28 also potentially increases debris generation; forexample, increased transverse movement at the cutting tip 28 translatesinto increased transverse movement of the inner wire assembly 26 withinthe outer tube 22, thereby increasing contact and/or contact forcesbetween the inner wire assembly 26 and the inner surface 52 of the outertube 22 and/or the inner surface of the bearing sleeve 24. Furthermore,such vibration and added contact can also result in an undesirableincrease in temperature due to frictional effects.

With the above in mind, the bearing sleeve 24 is adapted to reduceundesirable vibrational movement at the tip 28, for example by servingas a vibrational dampener. In particular, the bearing sleeve 24 isoptionally formed of a vibrational dampening material, such as arelatively softer material than a material of the distal region 46 ofthe outer tube 22. Debris from the outer tube 22 and/or inner wireassembly 26 are also reduced via use of the bearing sleeve 24. Forexample, with configurations in which the distal section 72 and theouter tube 22 come into contact, the potential for debris comprisingparticles of the outer tube 22 and/or distal section 72 of the innerwire assembly 26 exists. However, where the bearing sleeve 24 is used tomaintain the distal section 72 of the inner wire assembly 26, overalldebris from the outer tube 22 and/or inner wire assembly 26 can bereduced, for example by forming the bearing sleeve 24 of a relativelysoft material in comparison to the inner wire assembly 26, such as PEEKmaterials, for example. Such relatively softer, or more forgiving,materials can be used to reduce abrasion and/or impact forces fromtransverse movement at the distal section 72 of the inner wire assembly26.

In some embodiments, design features of the surgical cutting instrument20, such as material selection and the resultant journal bearing, allowfor limited exposure of the inner wire assembly 26 distal the distal end42 of the outer tube 22, represented at B in FIG. 4. For example, theexposed length B of the inner wire assembly 26 is not greater than about0.1 inch (about 2.54 mm); as another example, the exposed length B isnot greater than about 0.05 inch (about 1.3 mm), it being understoodthat other dimensions are contemplated.

With reference to FIG. 1, upon assembly, the proximal section 70 of theinner wire assembly 26 is generally disposed in the proximal region 44of the outer tube 22, and extends from the distal end 42 thereof. Theouter tube lumen 50 (FIG. 3) at the proximal region 44 is, in oneembodiment, substantially linear such that the proximal section 70 ofthe inner wire assembly 26 is supported in a linear configurationsubstantially free of bends or curves. As alluded to above, the proximalsection 70 of the inner wire assembly 26 can be substantially thicker indiameter than the intermediate section 74, such that the proximalsection 70 is more structurally rigid than the intermediate section 74,and thus more suited to rotation within a substantially linear, orstraight, portion of the outer tube 22. A more structurally rigid designat the proximal section 70 is advantageous in many respects. Forexample, the proximal section 70 is can be more resistant to torsion,flexing, or bending when a rotational force is being imparted on theinner wire assembly 26 via the motor (not shown).

In turn, at least a portion of the intermediate section 74 of the innerwire assembly 26 can be disposed in the intermediate region 48 of theouter tube 22. For example, where the curved segment 54 of the outertube 22 is located at the intermediate region 48, the intermediatesection 74 of the inner wire assembly 26 extends through the curvedsegment 54 (or segments) and also takes on a curved shape. Inparticular, the intermediate section 74 is adapted to be rotated in theouter tube 22 while maintaining the curved shape. As previouslydescribed, the intermediate section 74 has a substantially smallerdiameter than the proximal section 72 such that the intermediate section74 defines a substantially greater diametric clearance with the outertube 22 than a diametric clearance between the outer tube 22 and theproximal section 72. As a result, the potential for binding or unwantedinterference between the inner wire assembly intermediate section 74 andthe outer tube intermediate region 48, due to their respective curvedshapes, for example, is reduced. Additionally, where provided, thesmaller diameter of the intermediate section 74 can help to increaseflexibility of the intermediate section 74, thereby also reducing thepotential for binding or other unwanted interference between the outertube 22 and the inner wire assembly 26.

The outer tube 22 is assembled to the housing 32 with the intermediateregion 48 and the distal region 46 extending distal the housing 32. Aspreviously described, the housing 32 can be insert molded over the outertube 22, with the inner wire assembly 26 then being placed within thelumen 50. In some embodiments, the optional shoulder 56 of theintermediate region 48 provides a stop surface for positioning againstthe housing 32 if desired.

With reference to FIG. 5, in some embodiments the coupling chuck 30 issecured to the proximal section 70 of the inner wire assembly 26 byresistance welding. In particular, a first electrode E₁ and a secondelectrode E₂ are optionally used to weld the inner wire assembly 26 tothe coupling chuck 30 with a portion of the proximal section 70protruding from, or also, substantially coterminous with, the proximalend 80 of the coupling chuck 30. The weld joint is created by applyingvoltage to the electrode E₁. A relatively large electrical currentpasses from the first electrode E₁, through the coupling chuck 30 andthe proximal section 70 of the inner wire assembly 26, and to the secondelectrode E₂. The current heats the coupling chuck 30/inner wireassembly 26 to the point where the material between the electrodes E₁and E₂ softens; upon cooling and hardening, a welded joint is formed.However, other methods of connecting the wire assembly 26 to thecoupling chuck 30, such as via crimping, are also contemplated.

The manner of assembly using resistance welding is advantageous in manyrespects. For example, using crimping in the absence of resistancewelding, the proximal section 70 of the inner wire assembly 26 definesopposing flats (not shown) that are aligned to crimping points of thecoupling chuck 30 prior to crimping. Further, the second passage 90 isclosed, or is otherwise a “blind hole.” A user performing thecrimping-type assembly ensures that the proximal section 70 is fullyinserted into the second passage 90, ensures that the inner wire flatsare aligned, or properly indexed, to the crimping points, then stakes,or secures, the coupling chuck 30 and the inner wire assembly 26 in thatposition, and ultimately uses a crimping tool or machine to crimp thecoupling chuck 30 to the inner wire assembly 26. From this, it should beunderstood that more potential for user-induced inefficiencies exist. Inparticular, such methodology, including alignment steps, can be highlyuser dependent.

On the other hand, with resistance welding, the proximal section 70 ofthe inner wire assembly 26 is inserted into the second passage 90 of thecoupling chuck 30 and extends proximally from the coupling chuck 30. Inthis manner, the user performing assembly is able to better ensure thatthe proximal section 70 has been properly inserted into the couplingchuck 30. Further, resistance welding forms a substantially strongerconnection between the inner wire assembly 26 and the coupling chuck 30.In particular, an actual weld of material is formed, rather thangeneration of a mechanical interference, or crimp. However, crimping,resistance welding, or other methods of connecting the inner wireassembly 26 to the coupling chuck 30 are all within the scope of thepresent invention.

With reference to FIG. 4, the cutting tip 28 is attached to the distalsection 72 of the inner wire assembly 26. The cutting tip 28 can besecured to the distal section 72 via a variety of means, includingbrazing, laser welding, adhesives, threads or screw means, and othermeans for connecting or fastening, including those already describedabove. Alternatively, the cutting tip 28 can be substantiallycontinuously formed with the distal section 72 (see, e.g., surgicalcutting instrument 120 of FIG. 6).

Returning to FIG. 1, during use, a motor (not shown) is connected to thehousing 32, with the drive mechanism (not shown) connected to thecoupling chuck 30. The motor is then operated to rotate the couplingchuck 30 and thus the inner wire assembly 26. Rotation of the inner wireassembly 26 relative to the outer tube 22 can create a rotating journalbearing between the inner wire assembly 26 and the inner surface 52(FIG. 2) of the outer tube 22 along at least a portion of a length ofthe outer tube 22. For example, a journal bearing can be formed betweenthe proximal section 70 of the inner wire assembly 26 and the proximalregion 44 of the outer tube 22. Additionally, a journal bearing isoptionally generated between the inner wire assembly 26 and the bearingsleeve 24. If desired, a journal bearing can also be formed between theintermediate section 74 of the inner wire assembly 26 and the outer tube22.

Where provided, the lubricant, for example a grease lubricant, cangenerate a hydrodynamic journal bearing and/or combination rotating andhydrodynamic journal bearing between the inner wire assembly 26 and theinner surface 52 of the outer tube 22 upon rotation of the inner wireassembly 26. The lubricant also optionally forms a hydrodynamic journalbearing and/or combination rotating and hydrodynamic journal bearingbetween the inner wire assembly 26 and the bearing sleeve 24 uponrotation of the inner wire assembly 26. Regardless, some configurationsinclude the surgical cutting instrument 20 being characterized by theabsence of a ball bearing assembly between the outer tube 22 and theinner wire assembly 26.

The surgical cutting instrument 20 of the present invention is capableof maintaining its structural integrity at highly elevated rotationalspeeds. For example, the surgical cutting instrument 20 is operated atrotational speeds in excess of 50,000 RPM, such as about 80,000 RPM, asdesired. Further, embodiments where the inner wire assembly 26 is formedof M2 tool steel, the inner surface 52 of the outer tube 22 is highlypolished, and a grease lubricant is disposed between the inner wireassembly 26 and the inner surface 52 of the outer tube 22, have beensurprisingly found to provide many advantages. For example, suchconfigurations allow the outer tube 22/inner wire assembly 26 to includethe curved segment 54 extending through a radius of curvature such thatthe proximal region 44 and the distal region 46 extend at an angularoffset A of about 15°, for example, although other dimension arecontemplated.

Thus, the resultant surgical cutting instrument 20 facilitate high-speedsurgical cutting procedures with minimal interference to the surgeon'svisibility via the small outer diameter and/or curved nature of theouter tube 22/inner wire assembly 26. The minimal heat generationrenders the surgical cutting instrument 20 highly safe for virtually allsurgical applications, as does the minimal exposed length B of the innerwire assembly 26. Further, the outer tube 22 is highly stiff, greatlypromoting handling and use during a surgical procedure. Theabove-described performance attributes are optionally further improvedwith a hardened material coating (e.g., diamond-like coating) on theinner wire assembly 26. While each of the above-described features(e.g., material selections, processing, and lubricant selection) have asynergistic effect in producing a viable, high speed, low profile,curved surgical cutting instrument, variations on one or more of thesefeatures can be employed and remain within the scope of the presentinvention.

For example, an alternative surgical cutting instrument 120 inaccordance with principles of the present invention is described withreference to FIG. 6. In general terms, the surgical cutting instrument120 includes features and operates according to principles substantiallysimilar to those described in association the surgical cuttinginstrument 20 (FIG. 1). With this in mind, the surgical cuttinginstrument 120 includes a support tube 122, a bearing sleeve 124, aninner wire assembly 126, a cutting tip 128, a coupling chuck 130, ahousing 132, and an evaporative cooling sleeve 134. Similar to thesurgical cutting instrument 20, the inner wire assembly 126 is coaxiallydisposed within a lumen 150 (FIG. 7) formed by the outer tube 122, withthe outer tube 122 including at least one curved segment 154.

The outer tube 122 defines a proximal end 140, a distal end 142 (FIG.7), a proximal region 144 terminating at the proximal end 140 and adistal region 146 terminating at the distal end 142. The outer tube 122also includes an intermediate region 148 extending between the proximaland distal regions 144, 146. The outer tube 122 defines one or moreinner diameters with the lumen 150 extending from the proximal end 140to the distal end 142 of the outer tube 122.

The outer tube 122 can define a curved profile (e.g., the curved segment154) at or along the intermediate region 148. With a curved or bentprofile, the distal region 146 is angularly offset from the proximalregion 144. As described in association with the surgical cuttinginstrument 20, the outer tube 22 is optionally constructed to facilitateformation of a rotating journal bearing (i.e., frictional slidingjournal bearing) relative to the inner wire assembly 126 in conjunctionwith a curved construction. Alternatively, the outer tube 122 can bestraight.

With reference to FIG. 7, the outer tube 122 defines, in someembodiments, three inner diameters at the lumen 150. For example, thelumen 150 includes a first segment 160 at a first diameter, a secondsegment 162 at a second diameter, and a third segment 163 at a thirddiameter. The first segment 160 originates at the distal end 142 andextends proximally through the distal region 146. The second segment 162extends proximally from the first segment 160 toward the intermediateregion 148. The third segment 163 proximally from the second segment 162through the intermediate region 148 and the proximal region 144 to theproximal end 140 (FIG. 5).

The first segment 160, including the first diameter, can be adapted toreceive at least a portion of the bearing sleeve 124. For example, thefirst segment 160 is optionally sized and shaped, or otherwise adapted,to receive the bearing sleeve 124 in a press fit. The second and thirdsegments 162, 163 are sized and shaped, or otherwise adapted, to receivea portion of the inner wire assembly 126. By way of reference, in onenon-limiting embodiment, the first segment 160 has a diameter of about0.060 inch (1.52 mm). It should be understood that a number of otherdimensions (greater or lesser) are also contemplated.

The bearing sleeve 124 is substantially similar to the bearing sleeve 24(FIG. 2) previously described. The bearing sleeve 124 defines a proximalterminus 164 and a distal terminus 166 with an inner passage 168extending from the proximal terminus 164 to the distal terminus 166.Generally, the bearing sleeve 124 defines a bearing surface along theinner passage 168. Additionally, the bearing sleeve 124 is adapted to beinserted into the outer tube lumen 150 at the distal end 142 of theouter tube 122. For example, the bearing sleeve 124 is optionallyadapted to be press fit, or otherwise define an interference fit, withinthe outer tube lumen 150 at the distal end 142 of the outer tube 122.

With reference to FIG. 6, the inner wire assembly 126 defines a proximalsection 170, a distal section 172, and an intermediate section 174, theintermediate section 174 between the proximal section 170 and the distalsection 172. As described above with reference to the surgical cuttinginstrument 20 (FIG. 2), the intermediate section 174 can be moreflexible than at least one of the proximal section 170 and the distalsection 172. For example, the intermediate section 174 optionallydefines a substantially smaller diameter than, and/or is formed of amaterial(s) different from, one or both of the proximal section 170 andthe distal section 172 in order to provide relatively more flexibilityto the intermediate section 174.

With reference to FIG. 7, the cutting tip 128 is substantially similarto the cutting tip 28 (FIG. 1) previously described, and includes acutting bur 176 and an attachment end 178. In some embodiments, thedistal section 172 of the inner wire assembly 126 is connected to theattachment end 178 by integrally forming the distal section 172 of theinner wire assembly 126 and the cutting tip 128 as shown. For example,the inner wire assembly 126 and the cutting tip 128 can be machined froma single piece of stock material. However, other methods of connectionare also contemplated. For example, the cutting tip 128 can beseparately formed and subsequently attached to a wire otherwise defininga remainder of the inner wire assembly 126.

With reference to FIGS. 6 and 7, the coupling chuck 130, the housing132, and the evaporative cooling sleeve 134 are substantially similar tothe coupling chuck 30, the housing 32, and the evaporative coolingsleeve 34 (FIG. 2), respectively. In general terms, assembly of thesurgical cutting device 120 includes disposing the bearing sleeve 124 inthe outer tube lumen 150. In turn, the inner wire assembly 126 iscoaxially disposed in the outer tube 122 and the bearing sleeve 124 (assecured in the outer tube 122). A portion of the proximal section 170 ofthe inner wire assembly 126 projects proximally from the proximal end140 of the outer tube 122 and a portion of the distal section 172projects distally from the distal end 142 of the outer tube 122 with thecutting tip 128 secured thereto. The evaporative cooling sleeve 134 isoptionally provided and is secured or formed about the outer tube 122.The housing 132 receives and maintains the proximal region 144 of theouter tube 122 and the coupling chuck 130, with the coupling chuck 130connected to the proximal section 170 of the inner wire assembly 126.

The assembly of the surgical cutting instrument 120 toward the distalregion 146 of the outer tube 122 is described in more detail withreference to FIG. 7. As previously described, the bearing sleeve 124 isdisposed in the first segment 160 of the outer tube lumen 150. Forexample, the bearing sleeve 124 is optionally substantially the samelength as the first segment 160 of the lumen 150 such that when thebearing sleeve 124 is inserted into the outer tube lumen 150, thebearing sleeve 124 and the distal end 142 of the outer tube 122 aresubstantially coterminous. In turn, at least a portion of the distalsection 172 of the inner wire assembly 126 is disposed in the innerpassage 168 of the bearing sleeve 124 and extends distally from theouter tube 122 and the bearing sleeve 124. The distal section 172 of theinner wire assembly 126 can be maintained by the bearing sleeve 124 suchthat the distal section 172 of the inner wire assembly 126 does notcontact the inner surface 152 of the outer tube 122 upon rotation of theinner wire assembly 126 and/or while the inner wire assembly 126 isstationary.

For example, although the distal section 172 of the inner wire assembly126 projects proximally from the bearing sleeve 124 into the secondsegment 162 of the outer tube lumen 150, the bearing sleeve 124 servesto maintain the distal section 172 of inner wire assembly 126 such thatany contact (incidental or intentional) is at the interface between thebearing sleeve 124 and the distal section 172, rather than contactbetween outer tube 122 and the distal section 172. In particular, theinner passage 168 of the bearing sleeve 124 defines a smaller diameterthan the second diameter of the lumen second segment 162. In thismanner, the effective inner diameter includes a step from the innerpassage 168 to the second segment 162 of the outer tube lumen 150. Astepwise or other type of increase in relative size of the seconddiameter relative to the diameter of the inner passage 168 helps ensurethat the distal section 172 is maintained by the bearing sleeve 124rather than being supported directly by the outer tube 122. For example,the third diameter of the third segment 163 of the outer tube lumen 150is stepped down in size relative to the second segment 162. This helpsensure that the distal section 172 of the inner wire assembly 126 doesnot bind or otherwise undesirably interfere with the outer tube 122.

The distal section 172 of the inner wire assembly 126 is supported bythe bearing sleeve 124 in a substantially linear configuration, or isotherwise free of overt bends or curves. As alluded to above, the distalsection 172 of the inner wire assembly 126 can be substantially thickerin diameter than the intermediate section 174, such that the distalsection 172 and the proximal section 174 are more rigid than theintermediate section 174, and thus provide greater structural strengthand are more suited to rotation within a substantially linear, orstraight, portion of the outer tube 122. As previously described, theintermediate section 174 can be substantially thinner, and thereforeable to flex more easily. As such, the intermediate section 174 adaptedto extend through one or more curved segments of the outer tube 122,such as the curved segment 154, and adapted to be rotated thereinwithout undue fatiguing or resistance to rotation.

Another surgical cutting instrument 220 in accordance with principlesthe present invention is described with reference to FIG. 8. The cuttinginstrument 220 is similar to previous embodiments and includes an outertube 222, an inner wire assembly 226, a cutting tip 228, a couplingchuck 230, and a housing 232. Once again, the inner wire assembly 226 iscoaxially disposed within a lumen 250 formed by the outer tube 222 thatotherwise optionally includes a curved segment 254. Further, anintermediate tube 224 is disposed between the outer tube 222 and theinner wire assembly 226 along the curved segment 254.

The outer tube 222 optionally assumes any of the forms previouslydescribed with respect to the cutting instruments 20, 120 (FIGS. 1, 5),as can the coupling chuck 230 and the housing 232. The inner wireassembly 226 includes a first or proximal section 270 and a second orintermediate section 274. The first section 270 is optionally a rigidshaft or wire to which the coupling chuck 230 is secured or integrallyformed. The second section 274 extends distally from the first section270 and in some embodiments, is a spring wire akin to the inner wireassemblies 26, 126 previously described. That is to say, the secondsection 274 assume any of the forms previously described with respect tothe inner wire assemblies 26, 126. The first and second sections 270,274 can be separately formed and fastened together (e.g., laser weld,sintering, and others), or integrally formed from a single piece ofstock material. Regardless, in some embodiments, the second section 274defines a diameter less than that of the first section 270, having anaxial length substantially commensurate with an arc length of the curvedsegment 254 of the outer tube 222.

The cutting tip 228 can include a cutting bur 276 and a shaft 278. Theshaft 278 extends distally from the cutting bur 276 and is attached tothe second section 274 of the inner wire assembly 226. Also, the shaft278 can be formed as part of the inner wire assembly 226, for example asa distal section of the inner wire assembly 226, with the cutting bur276 subsequently attached thereto. For example, the shaft 278 isoptionally of an identical construction as the first section 270. Evenfurther, the cutting tip 228 and the inner wire assembly 226 can beintegrally formed. Regardless, the second section 274 is formed to havea diameter less than that of the shaft 278.

The diameter of the second section 274 can be smaller than that of thefirst section 270 and the shaft 278, as the second section 274 does notneed to support the bending load induced by the cutting bur 276. Thisconstruction has the potential for allowing a reduced radius secondsection 274 at the curved segment 254 (along which the second section274 resides upon final assembly) and serves to reduce the frictionload/heat in the curved segment 254.

The intermediate tube 224, also described as a bearing sleeve 224, isprovided between the second section 274 and the outer tube 222 tosupport the second section 274 upon rotation of the inner wire assembly226. The intermediate tube 224 can be formed of a PTFE material; also,other flexible tubing materials can be employed. The intermediate tube224 can be substantially inflexible and resistant to bending. Theintermediate tube 224 acts, with some configurations in accordance withprinciples of the present invention, to modify the effective innerdiameter of the outer tube 222, such that the effective inner diameterof the outer tube 222 is stepped down in the second section 274.

During use, the surgical cutting instrument 220 operates in a mannerhighly similar to previous embodiments. In particular, a motor (notshown) rotates the inner wire assembly 226 relative to the outer tube222 such that a rotating journal bearing is created between at least aportion of the inner wire assembly 226 and an inner surface 252 of theouter tube 222. A grease or other lubricant is optionally disposedbetween portions of the inner wire assembly 226 and the outer tube 222,for example along the first section 270 and/or the shaft 272 of thecutting tip 228 such that at high rotational speeds, a hydrodynamicbearing is established along the outer tube 222. Similar to previousembodiments, then, the surgical cutting instrument 220 is adapted toprovide a nominal rotational speed of 80,000 RPM with a low profile,curved outer tube 222 assembly.

Another surgical cutting instrument 320 in accordance with principles ofthe present invention is shown in FIGS. 9A and 9B. The surgical cuttinginstrument 320 incorporates sealing features which can be incorporatedinto one or more of the surgical cutting instruments described above tominimize flow of material into or out of the outer tube and/or act as abearing surface. For example, FIG. 9A is a side, cross-sectional view ofthe surgical cutting instrument 320 akin to embodiments described inassociation with the surgical cutting instruments 20, 120, 220. Thesurgical cutting instrument 320 includes an outer tube 322, a sealingtip 324, also described as a bearing sleeve 324, an inner wire assembly326, a cutting tip 328, a coupling chuck 330, and a housing 332. Thesealing tip 324 is attached to, and extends distally from, a distalregion 346 of the outer tube 322, and provides a bearing/sealing surfacethat more closely approximates an outer diameter of the inner wireassembly 326 of the surgical cutting instrument 320, thus limitingpossible intake and/or release of material from/to the surgical site.

The sealing tip 324 can be formed of a ceramic or polymer material, forexample sapphire, and exhibits enhanced hardness and surface finish ascompared to the outer tube 322. Thus, the sealing tip 324 has elevatedwear characteristics, increasing a life of a bearing formed between thesealing tip 324 and the inner wire assembly 326. Further, ceramicmaterials can be more readily manufactured to exacting tolerancerequirements as compared to steel (as is otherwise optionally used forthe outer tube 322) such that an inner lumen or inner passage 368 of thesealing tip 324 has a diameter less than a diameter of the lumen 350 ofthe outer tube 322, resulting in a reduced diametrical clearancerelative to the inner wire assembly 326. This reduced clearance, inturn, further prevents material from entering and/or exiting the outertube 322. For example, the lumen 368 of the sealing tip 324 can bemanufactured to provide a diametrical clearance relative to the innerwire assembly 326 in the range of from about 0.005 mm to about 0.01 mm,although other dimensions are also acceptable.

The sealing tip 324 can be assembled to the outer tube 322 in a varietyof fashions. For example, the outer tube 322 can form an internalaperture or counter-bore 360 at a distal end 342 thereof, having adiameter adapted to receive an outer diameter of the sealing tip 324 viaa close slip fit, or a press fit. With this configuration, an adhesiveor retaining compound (not shown) optionally secures the sealing tip 324to the outer tube 322. Regardless, in one embodiment, the sealing tip324 and/or the outer tube 322 are configured to provide a longitudinalinterface length of at least 1.5× a diameter of the sealing tip 324 tomaintain squareness and straightness. Because the sealing tip 324 islongitudinally straight, an overall length is optionally relativelyshort when employed with a curved configuration of the outer tube 322.To provide a sufficient bearing surface, the sealing tip 324 has alength in the range of from about 8 mm to about 14 mm although otherdimensions are contemplated. Finally, the sealing tip 324 has an outerdiameter commensurate with, optionally less than, that of the outer tube322, and can form a distal taper 363. For example, the sealing tip 324can taper from about 1.5 mm to about 2.5 mm in outer diameter, althoughother dimensions are also acceptable.

Embodiments of surgical cutting instruments of the present inventionprovides a marked improvement over previous designs. By eliminating aneed for a ball bearing assembly in conjunction with desired materialselections and processing techniques, the outer support tube can have anouter diameter significantly less than other available surgicalinstruments along with optimally located and sized curved section(s),while providing requisite stiffness. Further, material selection and,where desired, lubricant, allows for long-term high-speed rotation (onthe order of 80,000 RPM) with minimal instrument wear and heat build-up.Finally, embodiments of the surgical cutting instrument of the presentinvention require a minimal number of components, thus reducing costsand assembly time.

Due to the high speeds of operation, curved, low profile features,embodiments of the surgical cutting instrument of the present inventioncan be used in a wide variety of surgical applications. One field ofpossible applications includes numerous neuro-otology procedures, suchas cochlear implant, vestibular nerve section, facial nervedecompression, endolymphatic hydrops, and removal of tumors of the earincluding acoustic neuroma surgery (e.g., middle and posterior fossaapproaches), drainage of petrous apex cysts, and mastoidectomies, toname but a few. In addition, the surgical cutting instrument of thepresent invention can be used for a variety of other bodily procedures,such as those relating to sinus surgery, removal of bone spurs on thevertebrae, removal of arthritic bone spurs throughout the body, spinaldisc surgery, knee surgery, hip surgery, orthopedic surgical procedures,and others. In more general terms, the surgical cutting instrument canbe employed to remove, re-sect, cut, or debulk any bodily material(e.g., tissue, bone, etc.).

Embodiments of the high speed surgical cutting instrument of the presentinvention can be employed in the debulking and/or resecting of bone. Forexample, embodiments including a larger cutting tip (e.g., having adiameter of greater than about 2 mm, from about 3 mm to about 4 mm, orabout 3 mm or greater) can be employed to perform the debulkingoperation. It should also be understood that embodiments including suchlarger cutting can also be employed to perform a resecting operation ora portion thereof. Conversely, embodiments including a cutting tiphaving a diameter of about 2 mm or less can be employed to perform theresecting operation, or even the debulking operation or a portionthereof as desired. During debulking and/or resecting, the surgicalcutting instrument 20, 120, 220, 320 is deployed and operated (e.g., atspeeds of at least 50,000 RPM, including speeds of about 80,000 RPM) toresect/debulk the bone through the facial recess.

Embodiments of the surgical cutting instrument of the present inventionwith the curved configuration optionally protect the facial nerve as theouter tube extends into the facial recess, thus minimizing exposure ofthe facial nerve to the rotating inner wire that might otherwiseunexpectedly contact the facial nerve and/or cause thermal damage.Further, the curved, minimal outer diameter features of the surgicalcutting instrument of the present invention affords the surgeon vastlyimproved visibility of the surgical site as compared to conventionalcutting devices.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

What is claimed is:
 1. A method of performing a surgical drillingprocedure on bodily material at a target site of a patient, the methodcomprising: providing a surgical cutting instrument including an outertube, a bearing sleeve disposed in the outer tube, an inner wireassembly, and a cutting tip, the inner wire assembly being co-axiallydisposed within the outer tube and bearing sleeve and the cutting tipbeing connected to the inner wire assembly at a distal section andpositioned distal a distal end of the outer tube, the distal sectiondefining an outer diameter in a range of about 0.635 to 1.14 mm andwherein the cutting tip is a bur defining an outer dimension of not lessthan about 3 mm; exposing the bodily material at the target site;deploying the cutting tip against the bodily material; and rotating theinner wire assembly within the outer tube and the bearing sleeve suchthat a distal section of the inner wire assembly is maintained by thebearing sleeve and a proximal section of the inner wire assembly ismaintained by the outer tube to initiate a cutting interface between thecutting tip and the bodily material in contact therewith.
 2. The methodof claim 1, wherein the inner wire assembly is rotated at a speed of atleast about 50,000 RPM.
 3. The method of claim 1, further comprising:establishing a rotating journal bearing between at least one of theinner wire assembly and the outer tube, and the inner wire assembly andthe bearing sleeve upon rotating the inner wire assembly relative to theouter tube and the bearing sleeve.
 4. The method of claim 1, wherein theouter tube defines a curved segment.
 5. The method of claim 1, whereinthe method is performed as part of an acoustic neuroma surgery.